1. Field of the Invention
The present invention relates to a printed circuit board (PCB), a method of manufacturing the PCB, a memory module having the PCB, and a method of manufacturing the memory module. More particularly, the present invention relates to a PCB on which semiconductor packages are mounted, a method of manufacturing the PCB, a memory module having the PCB, and a method of manufacturing the memory module.
2. Description of the Related Art
Recently, as a speed of a central processing unit (CPU) has increased, there have been continuous endeavors to increase a speed and an integration degree of a main memory to improve a capacity of a system including the CPU. In order to increase input/output speed of data into/from the main memory, a bus structure capable of rapidly transmitting/receiving a packet can be arranged between the CPU and the main memory. Further, in order to increase a memory capacity of the main memory, a memory module including the memory that can be mounted on a printed circuit board (PCB) can be widely used.
The memory module can be classified into a single in-line memory module (SIMM) and a dual in-line memory module (DIMM). The SIMM can include semiconductor packages mounted on only one face of a PCB. In contrast, the DIMM can include semiconductor packages mounted on both faces of a PCB.
The main memory can have an increased memory capacity due to the memory module. Further, in order to improve the input/output speed of the data into/from the memory, it can be required to increase a transmission speed of the data by heightening a clock frequency of the memory. Furthermore, in order to provide the memory with a large capacity, it can be necessary to mount a plurality of the memory modules on a motherboard by increasing numbers of the memory module or numbers of slots in the motherboard.
However, when the clock frequency of the memory can be increased, the memory can have a reduced timing margin. Further, when the numbers of the slots can be increased, many loads can be generated on a transmission path of a signal, so that the signal transmission can become weak. In order to compensate the generation of the loads, a registered DIMM can be proposed.
The registered DIMM can include a phase locked loop (PLL), a register and a plurality of memories. When the registered DIMM is mounted on a motherboard, the generation of the loads can be compensated. However, when the slots are too many in number or the clock frequency can be too high, a reflective wave can be generated on the transmission path to reduce transmission efficiency.
To overcome the above-mentioned problems, a fully buffered DIMM (FBDIMM) can be proposed. The FBDIMM can include an advanced memory buffer (AMB) for providing external signals to the semiconductor packages. That is, in the FBDIMM, the external signals can be transmitted to the semiconductor packages via the AMB. Thus, signal lines through which the signals can flow can be connected to the AMB. Therefore, a burdensome load can be applied to the AMB. As a result, high heat can be generated from the AMB.
The high heat can shorten a life span of the AMB. Further, the high heat can badly affect operational reliability of the AMB. Thus, it can be required to rapidly dissipate the high heat from the AMB. Therefore, the AMB can include a heat spreader for dissipating the high heat from the AMB.
However, the heat spreader can increase a thickness of the memory module. Further, it can be required to perform additional processes for assembling the heat spreader into the memory module.